July 20, 2023

expert reaction to study looking at vegan, vegetarian, fish and meat diets in the UK and environmental impacts

A study published in Nature Food looks at the environmental impacts of vegans, vegetarians, fish-eaters and meat-eaters in the UK.

Prof Neil Ward, Professor of Rural and Regional Development, UEA, said:

“This is an interesting paper and a significant set of findings.  The press release is a good reflection of the science in the paper.  The research is published in Nature Food, which is a very high-quality scientific journal, and will have been subject to rigorous peer review.

“The study provides a stronger evidential base to support existing evidence which shows that meat-based diets have a significantly greater environmental impact than non-meat diets such as vegetarian and vegan diets.  The paper quantifies the difference in impacts, in terms of greenhouse gas emissions, between high-medium and low meat eaters and fish-eaters, vegetarians and vegans.  It demonstrates how high meat-eaters have an environmental impact four times higher than vegans.  It scientifically reinforces the point made by the Climate Change Committee and the National Food Strategy over recent years that dietary shifts away from animal-based foods can make a major contribution to reducing the UK’s environmental footprint and reducing greenhouse gas emissions.”

Prof Richard Tiffin, Professor of Applied Economics, and Chief Science Officer for Agrimetrics, University of Reading, said:

“This is a characteristically thorough investigation from these authors.  It represents the most comprehensive attempt to link food consumption data to the data on the environmental impacts of food production.  The results are provided with interval estimates which allow the reader to draw conclusions around the statistical significance of the differences reported.  Focussing on the two main greenhouse gases (CO2 and CH4) the results only show meaningful differences in emissions between the diets of high-meat-eaters and vegans.  For C02, the interval estimates for Vegetarians, Fish-Eaters, Low-Meat-Eaters and Medium-Meat-Eaters overlap to large degree suggesting that it is hard to make a policy recommendation regarding the merits of these different diets on the basis of the results here.  The degree of overlap is less for the CH4 results but the differences remain insignificant.  Overall therefore, encouraging high-meat-eaters to reduce meat consumption and encouraging vegetarians to become vegans should result in lower emissions.  However, it’s hard to justify changes to the diets of moderate omnivores (other than to switch to a completely vegan diet) on the basis of these results.”

Prof Eileen Wall, Head of Research, Scotland’s Rural College (SRUC), said:

“In an interesting article, this comprehensive analysis sheds light on the current available data, although the application of various lifecycle assessment methodologies from different countries to UK dietary information may not be ideal.  Figure 3 clearly demonstrates the uncertainty surrounding certain measures, as indicated by the error bars, particularly on some of the harder to define ecosystem service measures such a biodiversity.

“Different dietary choices will likely have different environmental impacts, and higher red meat consumption is likely to lead to a higher carbon footprint due to methane and grazing (and therefore N2O).  However, it’s important to note that red meat is a by-product of the dairy industry, presenting opportunities for optimisation within the dairy-to-meat supply chains.  Moreover, extensive farmland unsuitable for food or feed crops can be utilised for sheep and beef production, converting grass into a crucial component of the food basket and promoting a balanced diet.  Our grass-based production in the UK offers us an opportunity develop practices and policies that supports a socially, economically and environmentally sustainable food system.

“The study is detailed and focussed on environmental measures.  But our food system and subsequent food plate is more nuanced and with conflicting and sometimes confounding factors.  It’s worth considering the position of processed foods within this context – the paper used lifecycle assessments on the primary product/ingredient that the different diets represented, but each of those diet types can be defined by a range of ingredient types with knock on environmental NAD human health impacts.  It’s also worth considering the potential role of different land systems on rural (and urban) communities.”

Prof Dominic Moran, Professor of Agricultural and Resource Economics, Roslin Institute, University of Edinburgh, said:

Does the press release accurately reflect the science?

“Yes.

Is this good quality research?  Are the conclusions backed up by solid data?

“Good research and a large data set but basically confirming something we already know – meat intensive diets have high external costs.

How does this work fit with the existing evidence?

“As noted before – many many papers have compared diets and suggested that meat is emissions intensive plus demanding in terms of land use change and water.  There is some debate about attributing these impacts correctly in the supply chain and valuing them but that’s not really a big deal here.

Have the authors accounted for confounders?  Are there important limitations to be aware of?

“Not really any limitations without being pedantic.  Their data sample is impressive.

What are the implications in the real world?  Is there any overspeculation?

“Not too many that haven’t been said before – but a basic conclusion is that either (or both) producers and consumers need to pay the external costs of their diets.  Currently (apart from complete market abstention) there is no way for consumers to make the choices that allow them to avoid impacts and or to pay the external cost.”

‘Vegans, vegetarians, fish-eaters and meat-eaters in the UK show discrepant environmental impacts’ by Peter Scarborough et al. was published in Nature Food at 16:00 UK time on Thursday 20 July 2023.

DOI: 10.1038/s43016-023-00795-w

Declared interests

Prof Neil Ward: “No conflicts.

Professor Neil Ward, Tyndall Centre for Climate Research, University of East Anglia.

Neil Ward is a co-lead of UKRI’s AgriFood4NetZero (AFN) Network+, a network of 800 scientists and practitioners working to support the UK agri-food system through the net zero transition.

He is author of Net Zero, Food and Farming: Climate Change and the UK Agri-Food System (2023, Routledge.”

Prof Eileen Wall: “I’ve no conflicts with the authors of the paper.”

Prof Dominic Moran: “No conflicts of interest.

For all other experts, no reply to our request for DOIs was received.